In the wake of the Sep. 11, 2001 terrorist attack on the World Trade Center and the Pentagon, and the subsequent contamination of postal centers and other public buildings by anthrax spores and weapons grade anthrax aerosols, with associated deaths of postal workers and a recipient of a cross-contaminated letter, these tragic events have underlined our relative lack of rapid and effective detection protocols for both military and civilian populations. Furthermore, while it is possible to respond to a terrorist attack involving one known pathogen, such as anthrax, it is chilling to envision the potential chaos that might result from the simultaneous exposure of large segments of the general population to a multiplicity of pathogens, whether air-borne, water-borne or food-borne.
At the current time, there are no simple recognition systems that are particularly well suited to the simultaneous detection of multiple pathogenic agents. Nor are there rapid, reliable methods to identify the presence of these agents in the field, particularly for use by first responders (police, fire-fighters, paramedics, etc.). The current four-tier laboratory response network, designed to react to bioterrorism threats, proved woefully slow and cumbersome during the recent anthrax dispersion and hoax testing. For example, the first two tiers alone require at least 48 hours for identification of suspect pathogens. In addition, tiers three and four require even more sophisticated testing than tiers one and two, testing that must occur at more advanced centers, such as the Center for Disease Control and Prevention (CDC) and the US Army Medical Research Institute for Infectious Diseases (USAMRID). What is needed is a system that can be employed at the point of attack, operated by relatively untrained personnel (nonscientists), and that rapidly identifies a variety of bioterrorism agents. A recent report from NIH-NIAID (NIAID Biodefense Research Agenda for CDC Category A Agents, February 2002, National Institutes of Health) has identified a number of pathogens that are ideal bioterrorism agents, for example, tularemia, botulinum toxin, Yersinia pestus (plague), and smallpox. Notably, none of these agents are specifically detectable with currently existing detection systems.
Currently there are a wide variety of assays and sensors for the detection of the presence and/or concentration of specific substances in fluids and gases. Many of these assays and sensors rely on specific ligand/anti-ligand reactions as the mechanism of detection. In such methods, pairs of substances (i.e. the binding pairs or ligand/anti-ligands) are known to bind to each other, while binding little or not at all to other substances. For example, antibodies and their cognate antigens make up such a binding pair. Other ligand/anti-ligand binding pairs include complementary nucleic acids as well as the non-covalent interaction occurring between molecules such as biotin and streptavidin.
Detection of complexes comprising a ligand/anti-ligand binding pair is generally accomplished by labeling one component of the complex in some way, so as to make the entire complex detectable. For example, one component may be labeled with radioisotopes, fluorescent or other optically active molecules, enzymes, or virtually any other detectable moiety. In addition, other techniques are known that rely on the use of atomic force microscopy (AFM), surface plasmon resonance (SPR) or quartz crystal microbalance (QCM) systems as the means of detection.
An effective biosensor employing any of the described detection methods requires a robust flexible bioactive signal transduction system, such as one based on the attachment of specific antibodies or DNA probes to a biosensor surface. The instant invention provides multivalent dendrimer tether molecules with the capability of anchoring antibodies, or other binding moieties, to the surface of a biosensor, thus creating such a robust detection system. Furthermore, dendrimers, a class of monodisperse macromolecules with the advantage of multiple functionality, offer a number of synthetic design advantages that allow the attachment of binding moieties to a variety of surfaces to form effective biosensors (Dendrimers and Other Dendritic Polymers, J. M. J. Frechet and D. A. Tomalia, Eds., John Wiley & Sons, Ltd., Chichester, 2001; G. R. Newkome, C. N. Moorefield and F. Vogtle, “Dendrimers and Dendons: Concepts Syntheses and Applications”, Wiley-VCH, Weinheim, 2001; A. W. Bosman, H. M. Janssen and E. W. Meijer, “About Dendrimers: Structure, Physical Properties and Applications, Chem. Rev. 1999, 99, 1665–1688; 0. A. Matthews, A. N. Shipway and J. Fraser Stoddart, “Dendrimers-Branching Out From Curiosities Into New Technologies”, Prog. Polym. Sci. 1998, 23, 1–56. These new bioterrorism pathogen detectors are particularly well suited for use in AFM, as well as in SPR and QCM detector systems.